Blade propeller for submarine boats



G. AND U. ANTONI.

BLADE PHOPELLER FORSUBMARINE BOATS.

APPLICATION FILED MAE. H, 1915.

Patented Apr. 4, 1922.

UNITED STATES GUIDO ANTONI AND UGO ANTONI, OF PISA, ITALY.

Specification of Letters Patent.

BLADE PROPELLER FOR SUBMARINE BOATS.

Patented A r. 4,

Application filed March 11, 1915. Serial No. 13,675.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L, 1313.)

To all whom it may concern:

Be it known that we GUIoo AN'roNr andv Ueo AN'roNI, both subjects of the King of Italy, residing at Pisa, in the Kingdom of Italy, have invented new and useful Improvements in Blade Propellers for Submarine Boats, (for which we have filed application in Italy March 13, 1914, Patent No. 141,327,) of which the following is a specifilo cation.

This invention relates to blade or fish tail propellers such as are more particularly adapted for use in connection with submarines, and the object of the invention is to improve the structure and shape of the blade propellers shown and described in our Letters Patent of the United States No.

It has been found that while the rec- 2 tangular and trapezoidal blades constructed in accordance with our aforesaid Letters Patent give .very good results as regards the speed obtainable in raising or lowering a boat under the surface of the water they do not answer all practical requirements inasmuch as they are not conformed to resist the additional stresses arising when the boat is raised or lowered while it is being moved forward.

This disadvantage is obviated by the improved structure according to this inven-' tion.

In the accompanying drawingsi Figures 1, 2 and 3 are diagrammatic side views of blade propellers of the known type;

Figures 4 and 5 are similar views of blade propellers according to the invention.

Figure 1 shows a rectangular blade propeller having a section tapering from the lower edge toward the upper edge. The arrow A shows the direction of the thrust during the submerging of the boat, while the thrust of the screws which ensure the propulsion of the boat, is directed along B0.

It is obvious that the leading edge C D of the blade has to overcome the resistance of the water and is therefore subjected to a greater stress than the other parts of the blade. Experiments have shown that when the boat is given a horizontal motion,

the lines of deflection of the blade, that is to say the lines connecting the points corresponding to equal deflection of the blade, are not parallel to the axis or pivot The dotted lines in Figure 1 represent i the lines of deflection of the blade when the submerging takes place without longitudinal movement. Figure 2 illustrates the lines of deflection of the same blade when subjected to the resistance of: the water due to the longitudinal movement of the boat. The convergence of the lines of deflection at D gives rise to stresses which frequently cause the blade to break at that point.

In other known types of blade propellers the thickness of the blade not only decreases from the lowermost edge towards the upper-- most, as in Figures 1 and 2, but also from the leading edge towards the following edge (section my Fig. But these blades of trapezoidal shape also donot give satisfactory results, firstly because great diiiiculties due to the nonuniform. hardening of the steel in zones of varying thickness are encountered in the manufactureof such blades, and secondly because the simultaneous vertical and horizontal thrusts give rise to a component having approximately the direction of the arrow B (Fig. 3) which causes the lines of deflection to converge at M and the blade to be liable to break at that point. as explained above with reference to point D in Fig. 2. This action is still more marked when the boat is moved backwards. The various requirements are all met by the propeller designed in accordance with this invention which is shown in Fig. 4 and comprises a blade having a curved leading edge extending rearwardly fromthe forward end of lowermost edge 0 to the uppermost edge C. As in Fig. 1 the cross section of the plate tapers from the lowermost edge towards the uppermost, but the longitudinal section B-B' shows a uniform thickness.

The improved blade can be obtained from a rectangular blade by taking away a substantially triangular zone F. The exact shape of the curve C D is determined by the speed of the ship. The contour is always so designed as to obtain the greatest rigidity at D, the elasticity of the blade in creasing gradually from D towards C; the successive horizontal sections are all of rectan lar shape.

ith this conformation theections observed at D (Fig. 2) and M (Fig. v3.) no

longer take place. Further the blade can be manufactured easily as all the sections paralleltothe pivot have the same thickness and allow of a uniform hardening of the steel.

With this type of propeller forces may arise which ma deflect the component toward the bow see R", Fig. 4) during the submerging, butthese forces are negligible. The'formshown in Fig. 4 however does not allow of the boatbeing moved backwards without dan er of breaking the blade near the edge H53 When it is intended to provide for both forward and backward motion it is preferable to use a propeller such as shown in Fig. 5, which is symmetrical with respect to itsmiddle axis A S, the area Fand T 'on either side of the blade being equivalent. resist the stresses equally well when the boat is'moving forward or backward.

Having thus described our invention and how the same isto be carried into practice;

What We desire to protect by Letters Pat eat is:-

1. A flexible blade propeller comprising a blade supported along one of its edges and having a rectangular longitudinal section decreasin in length from. the supported edge to t e opposite edge. 7 p

2. A fiexib e blade propeller comprising a blade supported along one ofits edges and having a rectangular longitudinal section decreasing both in len h and width from the supported edge to t e oppsite edge.

3. A flexible blade propeller. comprising a substantially wedge-shaped blade supported along its thick edge and having a longitudinal cross-section of uniform thickness and a wldth increasing gradually from one A propeller of this form will from the front end of the said thick edge to a point on the opposite edge substantlally in the middle plane of the blade. 5

6. A flexible blade propeller comprising a substantially wedge-shaped blade mounted to swing about its thick edge and having curved front and rear edgesmeeting substantially in the middle plane of said blade.

7. A flexible blade propeller comprising a substantiall vwedge-shaped blade mounted to swing aiout'its thickedge, said blade having a longitudinal cross-section of uni form thickness and a curved leading edge extending rearwardly from the frontend of the said thick edge to a point on the opposite ed e substantially in the middle plane of the lade. f

8. A flexible blade propeller comprising a substantially wedge-shaped blade mounted to swing about its thick edge, said blade hav ing a longitudinal section of uniform thicke ness and ci'irvedlfront and rear edge meetin substantially in the middle plane of sai bla e. V

In testimony whereof Wehereunto aflix our signatures in the presence of two Witnesses. y

GUIDO ANTONI. UGO ANTONI. Witnesses ALFREDO CADDEI, GASTANO PAoiNoT'r. 

